My first post, but thought I would chime in on the thread. Another success story here.
I purchased a Raptor to get me closer to the back country for technical hiking and adventure. Furthermore, I needed a truck for pulling my camp trailer. I didn't do my research before my purchase, as I quickly realized the truck was poor at pulling trailers. The suspension and design was more for off road vs. towing. Stock, I lost > 4" on a 820 lb. tongue weight. In addition, I hit the bumps continually while loaded. In essence, it didn't work.
I then explored the various options. I spent hours researching. I was not happy with anything I found, as I didn't want to loose 1-2" with an airbag kit for example. Then I came across this thread...
I was able to get with Izzy in California to install the kit. You are looking > $3k for install, the nitrogen fill kit and tank. When I put the shocks in at 280 psi I drop about 1" now as compared to 4" without, at 820 lb. tongue weight. At 400 psi, perhaps a 1/4" drop. I take the shocks out most of the time to leave the truck as "stock". I happily put them in when hauling heavy loads.
Best upgrade...well the only upgrade, I've made. Given how much I spent on this truck for all the capabilities, it was worth the extra investment. At least for me.